Xerox Printed Memory (“XPM”) is a printed label that is capable of including rewritable memory. In one exemplary use, the labels may be used for testing to determine whether a product is faulty or functional, as well as authentic or genuine to prevent counterfeiting. For example, the printed memory may be attached as a label onto a consumable product, supply, shipment packaging, consumer product, document, customer-replaceable product, etc. Data from the printed memory may be read and compared to an expected result or value. If the value read from the printed memory by a memory reader matches the expected value, circuitry within the memory reader can identify the printed memory (and thus the item to which it is attached) as functional and/or authentic. In some uses, identification of the product as functional and/or authentic may be required before the product to which the printed memory is attached is allowed to function, in which case the memory reader, or a host device that incorporates the memory reader as a subsystem, can allow or enable functionality of the product. If the value read from the printed memory does not match the expected value, the circuitry within the reader or host device can designate the printed memory, and thus the item to which the printed memory is attached, as not functional and/or authentic, for example, as counterfeit, gray market, not manufactured by an original equipment manufacturer (“OEM”) or a licensed manufacturer (i.e., non-OEM), etc. In some uses, the memory reader or host device can disable functionality of the product if the label attached to the product is identified as not functional and/or authentic.
In another implementation, XPM may be used to track a product through a manufacturing process and/or a supply chain. The labels can be programmed to mark individual items with a unique electronic identifier that may be verified with a memory reading device. Other uses for XPM are contemplated including, but not limited to, smart consumables where an object is associated with data that is later used by a base unit to improve or optimize performance, consumption records where bulk usage of a product supply is tracked, tracking of items or people outside of a manufacturing environment, etc.
A XPM includes a layer of ferroelectric material (i.e., a ferroelectric layer) that uses the polarization of a cell as a data bit and is positioned between a plurality of wiring lines (e.g., word lines and bit lines). A region of the ferroelectric layer situated between each bit line (“BL”) and word line (“WL”) forms a memory cell. The memory may be written with one of two digital memory states by applying a suitable write voltage to the wiring lines. The memory state may be read by applying a suitable read voltage to the wiring lines through contact pads. If the polarization of the cell is in the opposite direction of the electric field from the applied bias, then, the polarization changes or flips direction inducing a current that gets integrated into a charge value. A cell that has its polarization vector already aligned with the electric field will not flip; hence, produces a smaller charge value equivalent to the capacitive charge value of the cell. Thus, by the very nature of the reading process the information on the chip is destroyed because at the end of the reading process the polarization of all the cells point into the same direction. This currently means 1 cell contains 1 bit. The cell is either polarized with the polarization pointing to the word line representing a 0 or in the opposite direction representing a 1. The existing XPM has a memory depth of 25 bits, or 25 ferroelectric cells. The simplified geometry of the XPM consists on tracing 5 bit lines across 5 word lines on opposite sides of ferroelectric material film thus forming a 5×5 array that yields the 25-bit memory depth.
Accordingly, what is needed is an improved method for writing to and reading from a XPM.